The eight generating stations in OPPD’s system are the work horses of the district, pumping electricity into the grid for our customers. Here’s a step-by-step look at how a coal-fired power plant works.
The coal arrives on a train car. One trainload of coal equals approximately 16,000 tons. For example, Nebraska City Station burns six to seven trainloads per week, while North Omaha Station burns two to three trainloads per week. In 2016, North Omaha Station’s Units 1-3 will be retired while Units 4 and 5 will be retrofitted with emission controls.
After being unloaded, the coal is moved up a conveyor belt, as needed, to the crusher house, where it is reduced to marble-size pieces.
The crushed coal then continues up the conveyor into the plant and stored in a bunker.
From the bunker, the coal passes through a pulverizer, where it is ground further until it is as fine as face powder. This makes the coal highly flammable, so it ignites and burns immediately when blown into the furnace.
The heat that is generated when the coal is burned in the furnace converts water in the boiler into steam.
Under tremendous pressure (2,415 PSI), the steam reaches a temperature of 1,000 degrees Fahrenheit. The pressurized steam is piped into the turbine, where it passes through a series of fan-like blades that cause the generator’s rotor to turn. This produces electricity.
From the generator, electricity flows to OPPD customers through a system of transformers and transmission lines.
The exhaust, or spent steam, passes over a series of tubes through which cool water from the Missouri River flows. The steam is condensed back to water and returned to the boiler. It is then reheated before going through the cycle again.
The river water, which is used only for cooling, is confined in a closed circuit. It is out of the river for less than 10 minutes before being returned. Environmental studies have shown no significant adverse environmental effects on the river.
Laura King-Homan is the managing editor of The Wire and a communications specialist at the Omaha Public Power District. She has nearly 20 years of print journalism and design experience, including the Omaha World-Herald.